Fungicides, as well as bactericides, are either chemical or biological agents used to protect agricultural crops from infectious pathogens which, if left uncontrolled, result in the weakening or destruction of a plant. In regards to agricultural crops, this is unacceptable, as economic losses will result. Specific pathogens which tend to have an undesired effect on various agricultural crops include Citrus Greasy Spot, Citrus Melanose, Oak Leaf Blister, Erwinia, Xanthomonas, and Alternaria. In the interest of protecting valuable agricultural crops, it is desired to have a fungicide and bactericide composition that readily eliminates or treats these various plant maladies, as well as other infectious agents.
Copper (Cu) compounds that are active as fungicides and bactericides have been in agricultural use since the advent of Bordeaux in the grape vineyards of France in the early 1800s. It has been observed that various types of copper compounds can be used to effectively treat various plant pathogens. As such, many different formulations of fungicides employing copper compounds, such as wettable powders, water based flowables, and dry flowables, are commonly used today in modern agricultural applications. While copper compounds are known to impart desirable fungicidal and bactericidal properties, there are associated problems. Specifically, known copper compounds are typically either phytotoxic, non-soluble, or ineffective as a fungicide or bactericide.
Generally, copper compounds used as fungicides have, for the most part, been inorganic in form when applied to agricultural uses. The inorganic copper compounds have been used because they have been observed to be non-phytotoxic. Organic forms of the copper compounds, while beneficially water soluble, have been found to be generally phytotoxic, especially in foliar applications.
Water soluble , copper compounds such as CuSO.sub.4, though effective to inhibit germination of fungus spores, cannot be used in foliar applications to agricultural crops because the cupric ion is extremely phytotoxic. Therefore, relatively insoluble forms of inorganic copper compounds, such as cupric hydroxide, have been found to be more effective fungicides. Note, however, that not all water insoluble Cu compounds are fungicidal or bactericidal. It is known that the in-vitro fungicidal activity is largely dependent on the copper solubility in the spore exudate and in the fungal cell. Also, despite the phytotoxicity, certain organic copper compounds have some utility as fungicides. An example of a suitable organic copper compound is CUTRINE (Cu salt of tri-ethanole amine) which is quite effective as an aquatic algicide, but unsuitable for use in other foliar applications.
While inorganic copper compounds are beneficially non-phytotoxic, they generally suffer from low water solubility. Modern day agricultural uses of inorganic copper compounds as fungicides employ varying forms of copper compounds having relatively low water solubility an d include, for example, cupric hydroxide, tri basic copper sulfate, and tank mix combinations (with heavy metal ethylene-bis-di-thiocarbamate fungicides to enhance the bactericidal activity against certain important agricultural bacterial such as Xanthomonas, Pseudomonas, and Erwinia). The lack of solubility of the inorganic copper compounds is an undesired problem. Because known and popular copper fungicides are largely water insoluble, they are normally applied in relatively large volume aqueous suspensions and, as such, are readily removed by rain after application. Frequent applications are, thus, necessary at short intervals--an application process which is expensive and environmentally imprudent.
Thus, both forms, inorganic and organic, suffer from problems. Therefore, the need exists for a highly water soluble Cu compound based fungicide and bactericide that is not phytotoxic. A need also exists for a water soluble Cu compound based fungicide and bactericide that reduces the adverse Cu load on the plant, thus reducing the non-target impact to the environment. Further, a need exists for such fungicidal and bactericidal compounds that permit use of other heavy metals such as manganese, zinc, iron, copper and mixtures thereof, as may be desired for specific fungicidal or bactericidal properties.